Many styles of gaming machines and games are known, including casual (or non-wagering) gaming and wager-based gaming. One popular style of game is the wager-based slot game. Slot games were originally presented by slot machines which utilized physical spinning reels to display a set of game symbols which defined the outcome of the game. Later, however, video slot machines were developed which display graphical representations of reels and associated slot symbols.
In order to make video slot games more exciting, various features have been added to those games. One popular and well known feature is the “expanding reel.” Normally a slot game is configured to display a fixed number of game symbols to a player, such as 15 symbols in the case of a 3×5 matrix of game symbol positions (5 reels each displaying a column of 3 symbols). In the case of the expanding reel feature, one or more additional symbol positions and game symbols may be displayed, such as disclosed in U.S. Pat. No. 6,544,120 (a trigger results in the display of additional symbols, thus extending existing pay lines or allowing additional pay lines), U.S. Pat. No. 8,602,059 (where the size of the symbol array may increase as a part of a mystery feature, thus allowing more pay lines) and U.S. Pat. No. 8,795,059 (where an increase in the size of a base array is indicated by the symbols displayed in that array), and U.S. Patent Application Publication No. 2016/0042597 (which describes a game area expander for expanding said game area in response to at least one predefined triggering criterion being satisfied, such that at least one additional symbol of the set of symbols is displayed in an expanded game area).
The expanding reel feature adds excitement because the addition of one or more game symbols to the set of displayed symbols may be used to form additional or different winning combinations of game symbols. While the expanding reel feature has been popular, it is well known and thus other innovative game features are desired in order to maintain the excitement of the game(s) and the interest of the players.